The present invention relates to a focus detecting device for use in a photographic camera.
Recently, there have been developed two typical focus detecting methods, one of which is a so-called upper-lower image coincidence method in which two oppositely polarized split images of an object created by the effect of wedge type prisms merge into a single image when the object is brought into focus, and the other of which is a so-called contrast method in which the contrast between mutually adjacent spot locations in the object's image becomes greatest when the image is in focus.
However, each of the aforesaid focus detecting methods has the disadvantage that it often results in an inaccurate focus detection or an erroneous focus detection in the worst case.